Two-stage smokeless incinerator

ABSTRACT

Effective incineration of waste products of various types is obtained by means of a two-stage grateless incinerator including a first stage vaporization zone with burner and forced air supply, and a second stage combustion zone with burner and forced air supply. The two-stage vaporization-combustion incinerator provides effective oxidative incineration, with gaseous products being smokeless, and any non-vaporized non-combusted solid matter is essentially retained in the first stage vaporization chamber.

United States Patent [4 Aug. 1, 1972 Pryor [54] TWO-STAGE SMOKELESS INCINERATOR [72] Inventor: Robert C. Pryor, Bartlesville, Okla. [73] Assignee: Phillips Petroleum Company [22] Filed: Oct. 8, 1970- [21] Appl, No.: 79,144

[52] US. Cl. ..110/8 A, 110/8 C 51 Int. Cl. ..F23g,5/12 [58] Field ofSearch ..ll0/7,8,8A,8C,18,18C

[56] References Cited v UNITED STATES PATENTS 3,552,331 l/l97l Widdig ..ll0/7 3,344,758 10/1967 Wotschke ..110/18 3,310,009 3/1967 Jacobs ..1 10/8 1,995,723 3/1935 VanDenburg ..110/8 3,417,717 12/1968 Jacobovici ..ll0/7 Primary Examiner-Kenneth W. Sprague Attorney-Young and Quigg [57] ABSTRACT 18 Claims, 2 Drawing Figures EXHAUST STACK WASTE 2 FEED-+ 5 PATENTEDAUE I I972 3.680.500

EXHAUST 1 STACK FUEL AIR 4 FE AIR I TIUEL [Ii 9 WASTE 2 11/1/1111 fl w L 8 E III/III III EXHAUST STACK AIR g SECOND STAGE BRTIEJ F/G. LFUEL INVENTOR. R C. PRYOR A TTORNEYS mt AVAILABLE COPY l TWO-STAGE SMOKELESS INCINERA'IDR This invention relates to an improved method of combustion of waste products. In a related aspect, the invention pertains to an improved smokeless incinerator.

Limited availability of land fills and dumping sites has meant increasing need for improved methods of incineration of a wide variety of waste and undesirable materials. Particularly needed are methods of incineration such that any solid non-combustible matter is retained in the incinerator and at the same time all volatile matter is as completely oxidized as possible and produced in gaseous evolution in smokeless form.

- The incinerator that I have invented and developed is particularly efi'ective in combusting difiicltly combustible material including chunk materials, high ash-content materials, and organic wastes of liquid, semi-solid, and solid form.

My invention provides a method and apparatus for effective incineration of difficultly combustible materials. My invention provides a method and apparatus which incinerates waste materials such that the gaseous products evolved therefrom are essentially smokeless. My invention further combusts combustible materials whereby non-combustible components are essentiall retained in the incinerator. I

Essentially, the incinerator of my invention is a twostage grateless incinerator. The first stage is a vaporization or volatilization stage achieved by directing a flame from a first burner together with forced air in a generally downward manner into the first stage, and onto the upper area or surfaces of the solid or semisolid materials to be combusted. Volatile matter is volatilized, some combustion occurs in this first chamber, and all gaseous products are conducted to a contiguous second stage in which further oxidation and combustion occur through the use of a second burner and further supply of forced air.

By virtue of the essentially surface vaporization in my first stage vaporization zone, there is no rush of gases through a body of waste material being incinerated, such as occurs in standard grate type incinerators. Therefore, there is minimum disturbance of the waste material itself, and thus minimum carry-over of relatively non-vaporizable particulate matter and if any, from the first blower or other forced air supply,

pass to the second stage combustion chamber where further flame from a second burner, and also further forced air supply where required, complete the oxidative-combustion process such that the final gaseous products from my incinerator are fully combusted and essentially smokeless.

My invention can be further visualized by reference to the accompanying schematic drawing. The drawing in FIG. 1 shows in elevation form the essential components of one embodiment of my incinerator, together with a side chute for waste material feed to the first stage.

FIG. 2 illustrates another embodiment of my incinerator together with a conveyor feed for waste materials, and also shows an optional heat conservation mode wherein the vaporous products of combustion are put through, for example, a waste heat boiler for production of steam. The latter, of course, is optional since the vaporous eflluent from my two-stage incinerator can be simply wastedwithout heat recovery.

In the embodiment of the incinerator of my invention shown in FIG. 1, waste materials 2 can be added directly to the first stage vaporization zone 1 by means of an access port such as chute 3 so as-to periodically or continuously move the waste materials 2 into the vaporization zone 1. In the vaporization zone 1, the waste materials 7 are subjected to high rate input of fuel 4 from at least one first burner 5 burning gas, fuel oil, or finely divided solid fuel such as powdered coal or coke, plus high rate input of forced air 6.

vaporization occurs in the case of solid wastes 7 in the first stage 1 essentiallyfrom the top of the waste material 7 downward. This aspect is important in my invention. The mass of waste material 7 itself is minimally disturbed since there-is no grate in the first stage zone 1. Therefore, no flow of air or other gaseous components occurs through the mass of waste material 7 to be incinerated. Hence, there is a very minimum, indeed negligible, transport of any solid relatively nonvaporizable particles from the first stage zone 1 on through the system of my incinerator. Thus, any such non-volatilizable components remain in zone 1. The components that do vaporize pass as vapor stream 8 including products of combusted fuel from the first burner 5 together with the excess of the first forced air supply 6 on to the second stage 9, where complete oxidative combustion occurs with an end result of minimal smoke formation.

In the first stage 1, fuel 4, optionally premixed with air 6 or other oxygen-containing gas, is burned in the first burner 5 which is illustratively posed with a generally vertically-directed combustion thrust downwardly toward and onto the waste material 7 positioned, in the case of solid and semi-solid material, in the lower portion of the first stage 1. The first burner or burners 5 optionally can be positioned at an angle or angles in the upper portion of the first stage 1 vaporization zone, so long as the major portion of the combustive thrust is generally downwardly toward the waste material 7 to be consumed. Forced air 6 can enter through or around the first burner 5 as shown. Optionally, additional or supplementary air can be separately blown or otherwise forced into the first stage 1 by way of one or more separate access ports or conduits. The first forced air supply 6 into and for the first stage 1 generally, though not necessarily, is over and above that necessary for simple combustion of the fuel supply to and in the one or more first burners, though the excess can be separately supplied if desired. The first forced air supply 6 may provide at least partial combustion in the first stage 1 vaporization zone, but primarily the purpose of first stage 1 is to provide a zone of high rate heat input so as to vaporize vaporizable components in the waste materials 7 to be consumed.

All gaseous products, including products of combustion of the fuel, excess air, vaporized waste, and any products of partial combustion in the first stage 1, form a gaseous stream 8 which is conducted by confined conduit to the second stage 9 combustion zone wherein primary oxidative combustion takes place.

In the second stage 9 combustion zone, additional fuel 11 is admitted to at leastone second burner 12, through and/or with which additional forced air supply 13 also is admitted to the second stage 9. Again, the separate second excess air supply 13 is intended to be over and above that necessary for combustion of the entering fuel supply 11 to the second burner 12, and preferably further is in considerable excess of that necessary for combustion of vaporized waste products. Such second excess air supply 13 is forced, for example, by blowing, into the second stage 9 combustion zone, and optionally can enter the second stage zone other than via burner 12. In the second stage combustion zone 9 all vaporizable components and oxidizable components received from the first stage 1 are fully combusted, i.e., oxidized as fully as possible, within the combustive influence of the second burner 12 and the second excess forced air supply 13, so that efiluent gases 14 exiting from the second stage 9 combustion zone to an exhaust stack 15 are essentially smokeless and indeed have minimal tendency toward atmospheric contamination.

In my FIG. 2 I show an embodiment similar to that as described relative to FIG. 1, a grateless dual zone incinerator, except showing a waste feed input by hopper 16 into conveyor 17, such as a screw conveyor for solid materials, to the first stage 1 vaporization zone. FIG. 2 illustrates that the efiluent gases 14 from the second stage 9 combustion zone are conveyed to an economizer such as a waste heat boiler 18 wherein such as a water-steam coil 19, shown by the dash lines is located, with water entering at 21 and steam exiting at 22. The exhaust gases then are passed finally to the atmosphere by means of stack 15.

FIG. 2 further illustrates that the second burner or burners 12 do not necessarily enter the second stage 9 combustion zone in a vertically upwardly projecting,

manner as illustrated in FIG. 1, but can enter at other than vertically upwardly, such as at an angle, or even horizontally as shown in FIG. 2. If desired, where multiple second stage burners are utilized, one or more can thrust upwardly, while another or others thrust more or less horizontally. The combustive thrust can be direct into the stage or wholly or in part tangentially, as may be preferred for maximum oxidative combustion.

In the operation of my incinerator, the first burner or burners and the second burner or burners 12 are ignited in any usual manner by suitable igniting devices,

and the injected combination of fuel and air for each burner is burned respectively in first stage 1 and second stage 9. A highly refractory protective lining is placed within each zone and through the conduit between the zones, and in the stack as necessary.

The temperatures in the respective zones depend on the material to be combusted, and can reach elevated temperatures in the range of 200 F. to 2400 F. or more in the first stage 1 vaporization zone, and even higher in relation thereto in the second stage oxidative combustion zone 9. The respective temperatures in the first stage 1 and the second stage 9 can be regulated by the respective degree or extent of firing and respective amounts of fuel 4 and 11 and air 6 and 13 to each burner 5 and 12. More easily volatilized components or materials in the first zone 1 can be volatilized at the lesser temperatures, with primary combustion then occurring in the second stage 9. More difficultly volatilized materials, of course, require higher temperatures in first stage 1.

I generally prefer to operate with a volume ratio of first zone to second zone of approximately 1 to 3, consider a volumetric ratio of about 122.5 as being a minimum, 1:3 as being preferred, and the ratio may extend upwardly toas much as 1:6 where additional volume in the second stage and stack are desired, or may even be required by certain legal restrictions concerning stack size and height.

In another and very useful embodiment of my invention, though not illustrated, the vaporization chamber for my incinerator is a trench formed or dug in strata of earth, or rock. The end wall of the trench is equipped with a suitably refractory-lined gas outlet pipe connecting with a suitably refractory-lined stack. The cover over the trench is an essentially double-wall metallic, ceramic, or metallic-ceramic structure through which air is force-circulated so as to cool the cover and in turn preheat the air. The preheated air then is used for the necessary combustion air and excess air supplies in both first and second stages. The primary burner or burners fire generally downwardly through the trench cover into the vaporization zone. The secondary burner or burners are located in the lower portion of the stack area, which is the second or combustion stage, and receive a portion of the preheated air which has been priorly circulated through the trench cover and fire additional fuel with tangential or upwardly directed combustive input. Waste products to be combusted are moved into this trench-type embodiment of my twostage grateless incinerator by truck or bulldozer and any final resulting ash is handled in a similar manner. Liquid wastes can be pumped or blown into the first stage. Finely divided wastes can be conveyor fed, or blown into the first stage.

As compared to the two-stage smokeless incinerator described relative to FIGS. 1 and 2, the trench-type embodiment does not require a refractory lining in the first stage vaporization zone. Instead, the first stage vaporization zone is the trench covered by the double wall structure which is cooled by the air circulated. In most areas of the United States, a suitable trench can be readily provided for the incinerator of the invention. The hot gases of combustion from the first stage and the directional firing in the second stage create sufficient draft so that there is no smoke escape from the open end of the first stage.

This trench-based embodiment of my invention particularly lends itself to effective disposal of large volumes of trash and waste of all types. Trucks and/or bulldozers can be used to move such wastes into the primary vaporization chamber and can also be used for removing the ash remaining after vaporization and oxidative combustion is complete, periodically, or even continuously, when the ash builds up to a sufficient height to require removal.

BEST AVAILABLE 'COPY The following examples will illustrate the effective- EXAMPLE In the two-stage smokeless incinerator of my invention utilized in incinerating materials as per runs shown in following paragraphs, the first zone was approximately 12 inches in diameter by 18 inches high, and had a volume of about 1.18 cu. ft. The second stage, in-

' cluding the stack, was approximately 6 inches in diameter and 20 feet high, and had a volume of about 3.87 cu.ft. Natural gas was utilized for the combustion of each sample, together with forced air supply to either wastes, specialized burners such as described in the copending Application Ser. No. 798,960, filed Feb. 13, 1969, by Robert C. Pryor et al., are useful in that while my incinerator incinerates the liquid and solid wastes, such burners incinerate the waste gases.

My invention is capable of reducing the weight and volume of trash and other waste materials to as little as 5 percent of the original weight and volume. It is apparent from my examples that incineration greatly reduces the disposal problem. Incineration also eliminates organic matter and odors associated therewith. Examples of materials that can be combusted without production of smoke include polyethylene pellets and other polyolefins, polyolefins containing ash or catalyst components, newspapers, garbage, rubber wastes, tire carcasses, oils, oils and solids even containing radioactive components, and car .qrb t wnas es bodies.

TABLE I Cu. it. of Burnin rate, Weight Ratio of air Sample natural gas On. it. lb.lhr. sq. ft. percent Maximum supplied to Zone RJHL size, (1,000 B.t.u. cu air/1b. bottom area of reduction temperature 1 :air supplied No. Conditions tt.)/lb. of waste of waste Zone 1 of waste attained, F. to Zone 2 1 Carbon black and tire tread rubber 11.5 482 23. 8 78. 3 2, 200 1. 58

scrap.

2 Solid polypropylene pellets 76 0 154 96. 7 100 2, 435 0.32 3 Kraft wrapping paper 7. 5 2.8 72 85 1,850 2.33 4 Carbon black pellets 10 440 6160 2. 56 100 2, 675 5 Polyethylene chunks 48 365 100 2, 400 0.67 6 A refinery asphalt emulsion. 41 3. 6 252 63. 6 98. 4 2, 640 0.50 7 Tetraethyl anhydrlde liquid 1. 3 0 163 99. 0 92. 6 2, 830 0. 65

1 All air to Zone 1, no air to Zone 2.

Runs 1 through 7 above represent a wide variety of waste materials that are effectively oxidatively incinerated in my two-stage smokeless grateless incinerator.

Certain waste materials, such as paper, carbon, garbage, and the like, can be completely or virtually completely burned in the first stage. Such materials ordinarily are slow-burning and require auxiliary fuel to start vaporization. An oxidizing atmosphere for such materials usually is maintained in the first stage by introduction thereto of a higher proportion of excess air.

Other waste materials, such as rubber, water-oil emulsions, and the like, cannot be completely burned in the first stage. Such materials are readily vaporizable, however, and require little in the way of auxiliary fuel into stage 1 to initiate and maintain vaporization. With such readily combusted materials, a reducing atmosphere usually results in the first stage, since even with high rates of air input, the oxygen consumption is so high that a reducing atmosphere is to be expected. Vaporized material from the first reducing atmosphere is to be expected. Vaporized material stage together with combustion products from the fuel combustion pass to the second stage oxidative combustion zone where additionaloxygen, usually in the form of air, is introduced with or without additional fuel as necessary so as to completely oxidize all materials present. With such waste materials, often the fuel requirements in the second stage are very low or even can be eliminated, simply supplying additional forced air to effect the desired oxidative combustion.

The burners useful in the first and second stages of the incinerator of my invention can be any suitable high combustion rate burners. Where disposal of waste gases additionally is desired, that is, in addition to or in conjunction with the afore described liquid arid solid least one second burner, at least one second forced air supply, entrance for receiving gaseous products from said first stage, outlet for combusted gaseous products from said second stage,

c. connecting conduit for conducting vaporous products from said first stage to said second stage qnfis swsea-w 2. The incinerator according to claim 1 wherein at least one said first burner is directed in a substantially downward direction from the upper area of said first stage downwardly toward the lower area of said first stage.

3. The incinerator according to claim 2 wherein at least one said first burner is directed downwardly in a u tant al y rsrti al esi s- 4. The incinerator according to claim 2 wherein at least one said second burner is in a substantially vertical position directing flame upwardly into said second stage.

5. The incinerator according to claim 2 wherein at least one said second burner is directed in a substantially horizontal position into said second stage.

6. The incinerator according to claim 2 wherein the volumetric ratio of the first stage to the second stage is from 1:25 to 1:6.

7. The incinerator according to claim 6 wherein the volumetric ratio of the first stage to the second stage is about1z3.

8. The incinerator according to claim 6 wherein said first stage is a trench of earth or rock.

9. The incinerator'according to claim 8 wherein said trench first stage covered a double-wall struc; ture open for passage therethrough of at least one of said first and second forced air supply.

7 10. The incinerator according to claim 6 wherein each said stage and said connecting conduit between said stages is lined with a refractory material.

11. The incinerator according to claim 10 wherein said vaporous effluent from said second stage is passed I through a waste heat recovery unit prior to exhaustion.

12. The incinerator according to claim 6 wherein said waste products include solids, semi-solids, and liquids, and are selected from amongst garbage, rubber wastes, tire carcasses, bus, paperfplasfics, and car bodies.

c. oxidatively combusting said vaporized components in said second stage in the presence of ex- 1 cess oxygen at an elevated temperature, and

d. exhausting the products of oxidativecombustion 1 from said step (c) to the atmosphere, and thereby converting said waste products into non-vaporizable components essentially retained in said first stage and an essentially smokeless essentially fully oxidized vaporous efifluent from said second stage. !9-..Ihs.n :9s aqq9 s tas si sllwh Said vaporizing step (a) is accomplished by heat produced by the combustion of at least one of a fuel and at least a portion of said waste products.

15. The process according to claim 13 wherein said excess oxygen is supplied in the form of forced air to at 5 least one of said steps (a) and (c), and said excess oxfygen is substantially in excess of combustive requirements of said fuel to said steps (a) and (c).

16. The process according to claim 15 wherein the temperature in said vaporizing step (a) is from 200' to 17. The process according to claim 16 wherein the A method of incinerafing waste Products-com 1 temperature in said oxidative combustion step (c) is prising the steps of:

a. vaporizing vaporizable components of said waste products in a first stage zone and substantially retaining therein non-vaporizable components of said waste products,

b. conducting said vaporized components from said step (a) by confined means to a second stage, 

1. A smokeless, grateless, two-stage contiguous incinerator comprising: a. a first stage comprising a vaporization zone, at least one first burner, at least one forced air supply, inlet for waste materials, outlet for gaseous products, b. a second stage comprising a combustion zone, at least one second burner, at least one second forced air supply, entrance for receiving gaseous products from said first stage, outlet for combusted gaseous products from said second stage, c. connecting conduit for conducting vaporous products from said first stage to said second stage by confined means.
 2. The incinerator according to claim 1 wherein at least one said first burner is directed in a substantially downward direction from the upper area of said first stage downwardly toward the lower area of said first stage.
 3. The incinerator according to claim 2 wherein at least one said first burner is directed downwardly in a substantially vertical position.
 4. The incinerator according to claim 2 wherein at least one said second burner is in a substantially vertical position directing flame upwardly into said second stage.
 5. The incinerator according to claim 2 wherein at least one said second burner is directed in a substantially horizontal position into said second stage.
 6. The incinerator according to claim 2 wherein the volumetric ratio of the first stage to the second stage is from 1:2.5 to 1:
 6. 7. The incinerator according to claim 6 wherein the volumetric ratiO of the first stage to the second stage is about 1:3.
 8. The incinerator according to claim 6 wherein said first stage is a trench of earth or rock.
 9. The incinerator according to claim 8 wherein said trench first stage is covered with a double-wall structure open for passage therethrough of at least one of said first and second forced air supply.
 10. The incinerator according to claim 6 wherein each said stage and said connecting conduit between said stages is lined with a refractory material.
 11. The incinerator according to claim 10 wherein said vaporous effluent from said second stage is passed through a waste heat recovery unit prior to exhaustion.
 12. The incinerator according to claim 6 wherein said waste products include solids, semi-solids, and liquids, and are selected from amongst garbage, rubber wastes, tire carcasses, oils, paper, plastics, and car bodies.
 13. A method of incinerating waste products comprising the steps of: a. vaporizing vaporizable components of said waste products in a first stage zone and substantially retaining therein non-vaporizable components of said waste products, b. conducting said vaporized components from said step (a) by confined means to a second stage, c. oxidatively combusting said vaporized components in said second stage in the presence of excess oxygen at an elevated temperature, and d. exhausting the products of oxidative combustion from said step (c) to the atmosphere, and thereby converting said waste products into non-vaporizable components essentially retained in said first stage and an essentially smokeless essentially fully oxidized vaporous effluent from said second stage.
 14. The process according to claim 13 wherein said vaporizing step (a) is accomplished by heat produced by the combustion of at least one of a fuel and at least a portion of said waste products.
 15. The process according to claim 13 wherein said excess oxygen is supplied in the form of forced air to at least one of said steps (a) and (c), and said excess oxygen is substantially in excess of combustive requirements of said fuel to said steps (a) and (c).
 16. The process according to claim 15 wherein the temperature in said vaporizing step (a) is from 200* to 2,400* F.
 17. The process according to claim 16 wherein the temperature in said oxidative combustion step (c) is substantially higher than said temperature in said vaporizing step (a).
 18. The process according to claim 17 wherein a volume ratio of said first stage to second stage is maintained at from 1:2.5 to 1:6. 